Regeneration of catalytic masses



Aug. l1, 1942. L. s. KASSEL l REGENERATION OF CATALYTIC MASSES 2Sheets-Sheet 1 Filed July 26, 1941 INVENTOR LOUES S. KASSEL.

ATTORNEY- Aug. 11, 1942.

L. S. KASSEL REGENERATION OF CATALYTIC MASSES Filed July 26, 1941 2Sheets-Sheet 2 Alwm , L.. Y N .0E E m S R R s o O A/ T m K /T :VL /zA WS/ E m3 S www m u .W0 L B m zudem .Qur Emis vm mm mmmzu \1 zormowmd 8 5mm m IA| n Y mm w/lobzum om E 2. NH12. di .un uw A1 n oh m ,m2 fuommzmuom uom ru w o mad. zomomr Patented Agg. 11, 1942 y vnncENrzmi'.r1oN orCATALYTIC MAssEs Louis ls. Kassel, chicago, 11i, assign to Univer- Dny,Chicago, Ill., a corsal Oil Products Com poration' of `Delaware.-Application July 2 6, 1,941, Serial No. 404,104 i 's claims.v (ci.y19e-52) i This invention relates to the catalyticconversion ofhydrocarbons and more particularly to a method of l regeneratingcarbonized catalytic masses.

In most of the catalytic hydrocarbon couver-f sion reactions fin whichliquidor vaporous hydro-- carbons are passed over a stationary bed ofgranular catalyst or other -solid vcatalytic material the periods ofori-stream time- This-decline in activity is a result of an accumulateddeposit of carbonaceous or hydrocarbonaceous material on the surface ofthe catalyst and it becomes necessary to regenerate the catalyst atperiodic intervals in order to maintain an elcient conversion y level.

It is with improvements in methods of regenerating vcarbonized catalystsfrom catalyticr conversion processes that my invention is concerned.

, As will be developed hereinafter in this specification, the object ofmy invention is to obviate a diiliculty commonly experienced inregenerating systems wherein the carbonized catalyst is regenerated insitu in the presence ofan oxygenvcontaining gas and the eiiluent gasesfrom the regeneration zone are recirculated.

In one specific embodiment my invention comv prises an improvementv inthe method of regenerating a body of carbonized catalyst materialwherein said carbonized catalytic material is subjected to contact withan oxygen-containing gas in a regenerating zone, a major portion of the-eiiiuent gases from said regenerating zone is mixed with a minorportion of an oxygen-containing the purge gas and the duration of thepurge pef catalyst tends to decline in activity after certain riod, adistilling eiect'also occurs whereby some lstream ofoxygen-free andrelatively linert gas. .such as nitrogen, flue gas, or in certain cases,

steam. This preliminary purging period is usually of only a few minutesduration and serves to sweepfrom the catalyst surface the more readilyremoved adsorbed hydrocarbons. To a slight extent, depending upon thetemperature of of the more strongly adsorbed hydrocarbons are removedfrom the catalyst interstices and swept from the reactor.

Following the purge period the regeneration 4or'otherwise swept from thecatalyst, and (2) by actual burning of the deposit which is controlledby the oxygen content of the regenerating gas stream. The two effectsmay occur at the same time especially .at dilerent points in a catalystbed. For example, when using a reactor oi' the type wherein the catalystis maintained as a gas, and the mixture is recirculated to the inlet ofsaid regenerating zone, said improvement comprising the step ofintroducing theY eiiiuent gases from'said regenerating zone into anabsorption zone containing thermally stable and relatively inertabsorptive material such as crushed rebrick, unglazed porcelain, crushedstone, absorptive clays, and similar substances, and adding said minorportion of oxygen-containing gas to the eiiiuent gases from saidregenerating zone prior to recirculation but after the passage of 'saideffluent gases through said absorption zone.

In order to explain the advantages and utility 'oi' my method-of,regeneration it is necessary to examine in 'considerable detail thenature of the regeneration process as commonly carried out.

In general, regeneration 'of carbonized catalystsv stationary bed andthe regenerating gas mixture is passed downwardly through the bed, itmay occur, especially at the beginning of a regenerating period, thatwhen using controlled amountsy of oxygen, such as one to two per cent,all the oxygen will be quickly consumed. and burning of the catalystdeposit will occur only in the upper portion of the reactor. The hot,substantially oxygen-free gases, however, pass through the lower portionof the catalyst bed and volatilize or otherwise remove certain heavierhydrocarbons in the catalyst deposit. It is apparent, then, that thisso-called distilling and purging effect which occurs along withcombustion of the deposit is considerably more extensive because of thehigher temperature and longer time than the similar eiect that takesplace during the preliminary purge period with .oxygen-free gases. y

As evidence that this eiect is a relatively important one, I, haveobserved :in experimental catalytic cracking units that the eiiluentA.regenerating gases often have a smoky dark appearance4 indicating thepresence of'con'siderable has been accomplished in approximately thefollowing manner. Immediately following the procperiod the catalyst bedis purged with a unoxidized or partially oxidized material. -In

many cases, heavy liquid hydrocarbons have been separated Afrom theeilluent gases :duringthe regeneration proper, and it is also common toDfind deposits of coke in the eiiiuent regenerating gas lines whichindicate that the heavy hydrocarbons from the catalyst deposit condensedon the cooler portions of the outlet lines and were eventually reducedto coke by the high temperature of the eiliuent gases at another time.

In certain catalystic conversion processes the nature of thehydrocarbonaceous material deposited on the catalyst is such that largeamounts of heavy hydrocarbons are swept from the reactor in relativelyunoxidlzed form as described above. If this material is recirculatedthrough heaters, heat exchangers, compressors, coolers, etc., anobjectionable gum-like or cokelike deposit is often left in lines,valves, and other points.

Moreover, if these heavy hydrocarbons are reclrculated and introducedinto the reactor with the regenerating gas stream, oxygen consumptionwill be materially increased and the regeneration will generally be mademore diicult because the recirculated combustible hydrocarbons will nowcompete with the hydrocarbonaceous deposit for the available oxygen inthe regenerating gas stream. In addition, the increased liberation ofheat will complicate the problem of maintaining the degree oftemperature control which is necessary to avoid damaging the catalyst orthe material of construction of the reactor. Usually it is desirable tohold the maximum regeneration temperature below about 1300 F.

Obviously, it is advantageous to remove these volatilized hydrocarbonsfrom the regenerating gas stream at some point between the dischargefrom the reactor and the point of introduction of the recirculatedgases. By my method of operation the eluent gases from the regeneratingzone are continuously passed through an adsorption zone wherein thevolatilized heavy hydrocarbons are absorbed before recirculation inorder to prevent objectionable gum or coke deposits in other parts ofthe system and in order to prevent said heavy hydrocarbons from beingreturned to the reactor and burned there with the liberation of heat.

The absorption zone or chamber is usually located immediately at theregenerating zone outlet, but it may be placed at any useful andconvenient point in the recirculating system as hereinafter described.Air or other oxygen-containing gases are continuously admitted to therecirculating system at a point after the gases have passed through theabsorption chamber. It is possible that in certain embodiments of myinvention, combustion may take place in the absorption chamber at timeswhen the eiiiuent regenerating gases from the reactor have asuiiiciently high temperature and oxygen concentrationand when theconcentration of combustible hydrocarbons in the absorption zone becomessufficiently high. However, as will become evident hereafter in thediscussion of Fig. 1 of the accompanying drawings, this is anundesirable condition which can be avoided by operating in the manner tobe described.

It is within the scope of my invention to employ spent catalyst in theabsorption chamber; i. e., catalyst which has been previously used inhydrocarbon conversion reactions or in other processes and whoseactivity has declined to an undesirableor uneconomical level. Thesiliceous or clayY supported catalysts comprising silica, alumina orother components which are Widely used in the cracking ofy hydrocarbonoils are well suited for the purposes of my invention, although ofcourse there are many others equally Well suited. It should beemphasized that I employ such spent catalysts merely for their physicalabsorptive properties.

Fig. 1 of the accompanying drawings diagrammatically illustrates anarrangement of apparatus for carrying out one embodiment of the processof my invention, and Fig. 2 diagrammatically illustrates anotherarrangement of apparatus for carying out a modified embodiment of theprocess of my invention.

Referring to Fig. 1, the reference numeral 3 indicates a catalyticreactor of any Well-known type in which catalyst is maintained as asolid continuous bed or in intermediate layers or in trays or in anyother suitable manner. A vaporized or partially vaporized hydrocarboncharge is admitted to the reactor through line I and valve 2. Thereaction products are removed from the reactor through line 4 and valve5 and discharged into a fractionator 6, of the conventional type..Ordinarily a light gasoline-containing distillate is removed overheadthrough line 1 and valve 8 to condenser 9. distillate andnon-condensable gases through line I0 and valve II to receiver I2.Pressure is ordinarily maintained on the system by withdrawing thenon-condensable gases through line I3 and valve I4. The liquid productmay be removed through line I5 and valve IB for storage or for anyfurther desired treatment. If desired, a portion of the liquidcondensate may be returned to the top of fractionator 6 by means, notshown, to act as a reuxing agent.

Reux condensate or other insufficiently converted material is removedfrom the fractionator through line I1 and valve I8. It is understood,oi' course, that this drawing is intended only to show the fundamentalsof a catalytic conversion process of this type. Therefore, the ultimatedisposal of a reflux condensate stream suc'h as the one last referred tois not indicated. Ordinarily, however, such a -stream might be recycledto another step in the process or used as charging material for anotherprocess or removed as a product of the present process. It is alsounderstood that in such a system a plurality of reactors or catalyticconverters is preferred in order that the conversion reaction may becarried out without interruption, each reactor being subjected toalternate periods of processing and regeneration. For the sake ofsimplicity, however, only a single reactor has been' shown in thedrawings.

After the reactor has been on process for a suitable length of time thecatalyst therein is regenerated by oxygen-containing regenerating gaseswhich are admitted to the reactor through line 28 and valve 29. Theproducts of the regeneration are removed from the reactor through line3| and valve 32. They are then directed through valve 33 to absorptionchamber 35 which is the feature of my invention. The heavy hydrocarbonmaterials which have been swept from the catalyst surface in relativelyunoxidized form are absorbed in chamber 35 and the remaining gases aredischarged from the chamber through lines 36 and 31 and valve 38. Thedischarged gases The condensed pass 2,292,599 I portant economic saving.The cooled gases leave through valve 42' and pass by line 43' tocompressor 2 3. The compressed gases are discharged through line 24 andvalve 25 intoheating coil 29 disposed in furnace 21; -The heated gasesthen pass through line 28 and valve 29 and are thus recirculated to theinlet of reactor 2.

VControlled amounts of air or other oxygencontaining gases areintroduced into the recirculating system through lin'e I9 and valve 2l.It

' is also necessary occasionally to supply relatively-small amounts offlue. gas or other oxygenfree regenerating gas through line 40 and valve4| in order 'to compensate for leakage in the system. This extraneousaddition of'ilue. gas may also be necessary for purging .purposes orwhen starting up a unit. Constant pressure is maintained in theregenerating system by means' of .vent line 48 and pressurecontrolv'alve 49 lthrough which gases are released corresponding to theaddition of air to the system through line i9.

vIn certain cases it may occur that after a reactor has been onregeneration for a considerable.

period of time the oxygen content of the eiiiuent regeneration gaseswill begin to build up because onlya small amount of combustiblematerial vremains on the catalyst. Aspreviously indicated,

if the temperature of the gases andthe concen-j tration of absorbedhydrocarbons in the absorpcracking process utilizing silica-alumina orsimilarcatalysts, I havey observed that the method of manufacture of thecatalyst has animportant ef- 1 fect on itsregeneration characteristics.Catalyst particles prepared by the mechanical extrusion oi' aprecipitated gel tend to regenerate in such a manner that appreciablequantities of oxygenappear in the eilluent regenerating gases arelatively short time after the regenerating period has begun. On'theother hand, catalyst particles of the'same composition, but prepared bya pillingoperation involving mechanical compression of a powder, haveentirely diilerentregeneration characteristics. With this type. ofcatalyst under certain conditions of pressure and moisture content ofthe regenerating gases it has been observed that the eiiiuentregenerating gases are approximately oxygen-free during substantiallythe entire regeneration period.

Referring now to the embodiment of my -invention illustrated in Fig. 2,the processing side vof the plant is the same as shown in Fig. 1. The

vaporized hydrocarbon charge enters reactor 52 through line 50containing valve" 5|. The .reaction products-passthrough line 53 andvalve 54 into fractionator 55. An overhead distillate andnon-condensable gases are removed through line i 56 and valve 51 tocondenser 58. The liquid contion chamber are suiiiciently high,combustion may take place when these high oxygen content gases areintroduced into the vabsorption zone. An obvious disadvantage wouldthereby result, namely, the fact that at least a portion of the absorbedhydrocarbonaceous material would be dis- 1 tilled or purged from the-absorptive agent because ofthe heat of burning and Athe volatilizedhydrocarbons would then be introduced into the recirculating system,thus counteracting in'part the utility ofthe entire invention. This undesirable feature may be eliminated by closing valves 33 and 38 and byopening valve 43. Thus the eiiluent gases from reactor 3 pass throughline 3i valve 32, line 42 and valve 43 and are then recirculated.

vDuring the time near the end ofthe regeneration period when itisnecessary to by-pass the absorption chamber, the absorptive materialitself may be regenerated in a manner similar to the regenerationof thecatalyst in reactor 3. This regeneration may be accomplished byintroducing heated air through line 44, valve 45 into absorption chamber35. The eiiluent gases from this regeneration are removedthrough-lines 36v and 46 and valve 41 and usually-vented to the densate and uncondensedgases pass through line 59.' and valve 60 into receiver 6l where theliquid product may be withdrawn by means of line 64 and valve 65 and thexed gases may be released through lines! and valve 53. A recycle streamof insufficiently converted material is' removed through line 66containing valve 61.

' The regenerating system of this particular embodiment of my invention,however, involves somewhat different features than those shown inFig. 1. V In this case. a flue gas generator or convertor 68 ismaintained wherein air and fuel gas are mixed and burned in order toproduce-a continuous supply of regenerating gas. Air is in- I troducedinto the generator through line 59 convtaining valve 'I0 and fuell isintroduced through line 'H containing valve 12. The regenerating gaswhichalso contains controlled quantities of oxygen as described laterpasses through line 'I3 and valve 14 into reactor 52 where regenerationof the catalyst occurs. Y

In this case the effluent regenerating gases from the reactor do notpass directly into the absorption chamber as in Fig. l. Instead, thegases are removedthrough line 15 and pass through line 16 containingvalvev 1 1 to a waste heat boiler 18.

This boiler may be of any well-known construction whereby the hotcombustion gases are used in the generation'of steam.A A portion of theheat .content of the eiliuent regenerating gases may bethereby'recovered in order to improve the overall economics of theprocess. Boiler feed water venters by line 99 and. valve |00 and steamis removed through line i0| and valve l102. Ihe outlet gases from thewaste heat boiler pass through line'91 and valve 98. The temperature ofthe outlet gases from the waste heat boiler may be controlledwithincertain limits by by- It shoum be realized that the desirabilityor` necessity for by-passing the absorption ,chamber 'las shown, in Fig.1 will depend-upon the Aregeneration characteristics fof .thejcatalystand-the catalyst deposit and upon the voperating'c'onditions under whichthe regeneration 'is carried boiler-18.

out.. For example, in the case -of a` catalytic 7 5'4 passing a portionof 'the eiiluent regenerating gases from vthe reactor around the wasteheat boiler. This' is accomplished by means of line 9 5 containing valve95.- It should be realizedthat .any-'well-known 'type of heat exchangeequipment may fbe'- utilized in place of waste-heat The combinedgaseousstreams pass through line 99 containing valve- 8 4 intoabsorption chamber 85. This chamber operates in the same nianner as theabsorption chamber of F18. l.- However, in this case sufiicient heat hasAbeen removed from the eiliuent regenerating gas stream by means of thewaste heaty boiler so that the temperature of the gases in theabsorption chamber is too low to initiate combustion of the absorbedhydrocarbons therein. Thus, even if an appreciable quantity of oxygen ispresent in the eiiiuent regenerating gases, no combustion will occur inthe absorption zone because of the low temperature. 'I'his temperaturewill normally be in the range of 700 to 900 F.

The hydrocarbon-free regenerating gases leave the absorption chamberthrough line 86 and valve 81 and pass into the suction side of acompressor or blower 89 which serves to recirculate the gases. Aspreviously indicated, excess air or other oxygen-containing gas 'isadmitted to the system through line 82 and valve 98 at the suction sideof the compressor or blower. It can be seen that absorption chamber 85serves as animportant protective device for the compressor or blowersince the gum forming hydrocarbons which would be detrimental to theoperation of this apparatus are thereby filtered out.

The oxygen-containing regenerating gases discharged from compressor orblower 89 pass through line 90 and valve 9i into the nue gas generatoror converter 88. In this zone the gases are re-heated to the desiredtemperature by means of the fuel combustion therein and additional gasis added to the stream if necessary. The gases are then recirculated tothe inlet of the reactor as previously described. Substantially constantpressure is usually maintained in the regenerating system by means ofvent line 8| containing valve 82. l

It should again be emphasized that Figs. 1 and 2 illustrate only twoparticular embodiments of my invention and that in no manner do I intendto restrict'my invention to the two process ilows shown. It is obviousthatthere are numerous arrangements of equipment and types of equipmentwhich may be utilized in catalyst regeneration systems and to which myinvention will be a useful and important addition.

I claim as my invention:

l. In the method of regenerating catalysts by removal of carbonaceousdeposits therefrom wherein a catalytic mass is regenerated in situ inthe presence of oxygen-containing gases and the effluent gases from thevregenerating zone are recirculated, with the addition of extraneousoxygen, to the inlet of said regenerating zone, the improvement whichcomprises passing the eiiluent gases from said regenerating zone.

generation zone are recirculated, with the addition of a minor portionof oxygen, to the inlet of said regeneration zone, the improvement whichcomprises first passing the eiiiuent gases from said regeneration zonethrough an absorption zone, without the addition of extraneous oxygen,wherein heavy hydrocarbons contained in said eiiluent gases are absorbedon a thermally stable and relatively inert absorbent material andwherein no substantial amount of combustion occurs, and finallyrecirculating the emuent gases from said absorption zone, with theaddition of extraneous oxygen, to the inlet of said regeneration zone.

3. In -a hydrocarbon conversion process wherein a catalytic mass isalternately subjected to processing by passing. hydrocarbon vapors oversaid catalytic mass at conversion conditions of temperature and pressure-and to regeneration by passing heated oxygen-containing gases over saidcatalytic mass and recirculating a major portion of the eiiluentregenerating gases with the addition of a minor portion of oxygen, theimprovement which comprises passing the ef- !luent gases from theregeneration zone through an absorption zone containing thermally stableand relatively inert absorptive material wherein heavy hydrocarbonspresent in said eiiiuent gases are absorbed prior to the addition ofextraneous oxygen andprior to the recirculation of said efiluentregenerating gases.

4. A process for regenerating catalytic masses having deposited thereonhydrocarbonaceous material comprising burning and purging of saidhydrocarbonaceous deposit with a mixture of air and products ofcombustion, passing the eiiiuent gases from the burning and purging zonethrough an absorption zone containing thermally stable and relativelyinert absorptive material wherein heavy hydrocarbons contained in saideiiiuent gases are absorbed and wherein no substantial amount ofcombustion occurs, and returning a' major portion of the eilluent gasesfrom said absorption zone to said burning and purging zone with theaddition of a controlled minor portion of air.

5. The process of claim 4 wherein said absorption zone is by-passed fromthe regenerating system during that portion of the regeneration periodwhen the efiiuent gases from said burning and purging zone containappreciable quantities of oxygen thereby avoiding any substantial amountof combustion in said absorption zone.

6. The process of claim 4 further characterized in that a substantialamount of heat is removed from the eiiiuent gases from said burning andpurging zone beforev the introduction of said gases into said absorptionzone.

LOUIS S. KASSEL.

